Drilling apparatus

Abstract

A drilling apparatus (1) is for use on a rotary drilling rig with a top drive which enables circulation and rotation of a drill string (3) to continue uninterrupted during the making of drill string connections. It has a snubber gripping mechanism (10, 9) to enable tool joints (2, 3) to be supported and gripped with a reduced pressure chamber (5) volume and snubbing force, during tool joint connections. The gripping mechanism has gripping pads (14) arranged to move radially by relative rotation of a drive cylinder (34) causing a tapered surface (36) of the drive cylinder (34) to press against or release the pad (14). A guide cylinder (30) supports and guides the pads (14) and collets (13) for retaining a drill string at an upset shoulder (19).

The invention claimed is: 
     
       1. A drilling apparatus for use on a rotary drilling rig with a top drive which enables circulation and rotation of a drill string having a longitudinal axial direction to continue uninterrupted during the making of drill string connections,
 the drilling apparatus comprising
 a tool joint gripping mechanism arranged to rotate at the same speed as the drill string and including: 
 gripping pads arranged to move radially relative to the drill string, said gripping pads being wedge-shaped, with a tapered surface upon which a gripping force is exerted and a contact surface for contacting the drill string and 
 a pad drive to drive the pads radially relative to the drill string, 
 collets arranged to engage and retain the drill string upset at a shoulder, 
 a collet drive arranged to move the collets radially with respect to the drill string, and 
 a guide cylinder having ports for the pads and for the collets, and being adapted to rotate the pads and the collets and to restrain the pads and the collets to move radially, 
 
 wherein the pad drive comprises a pad drive cylinder with an internal wedge profiles which, on rotation relative to the pads when it rotates faster or slower than the guide cylinder, moves the pads radially to engage or disengage the drill string. 
 
     
     
       2. The drilling apparatus as claimed in  claim 1 , wherein the collet drive comprises a collet drive cylinder with internal wedge profiles which, on rotation relative to the collets when it rotates faster or slower than the guide cylinder, moves the collets radially to engage or disengage the drill string. 
     
     
       3. The drilling apparatus as claimed in  claim 1 , wherein at least one of the drive cylinder and the guide comprises a flange which is engaged by a drive member to rotate. 
     
     
       4. The drilling apparatus as claimed in  claim 1 , wherein at least one of the drive cylinder and the guide comprises a flange which is engaged by a drive member to rotate, and wherein the drive member comprises a gear. 
     
     
       5. The drilling apparatus as claimed in  claim 1 , wherein the guide cylinder and the pad drive cylinder overlap in the radial direction. 
     
     
       6. The drilling apparatus as claimed in  claim 1 , wherein the guide includes guide rings and at least one drive shaft interconnecting said guide rings. 
     
     
       7. The drilling apparatus as claimed in  claim 1 , wherein at least one of said collets is adjacent to at least one of said pads in the axial direction. 
     
     
       8. The drilling apparatus as claimed in  claim 1 , wherein the collet drive and the pad drive are interconnected. 
     
     
       9. The drilling apparatus as claimed in  claim 1 , wherein:
 the apparatus comprises a pressure chamber and an upper gripping mechanism arranged to engage the drill string above the pressure chamber and a lower gripping mechanism arranged to engage the drill string below the pressure chamber; and wherein said gripping mechanisms are snubbers, or 
 the apparatus comprises a pressure chamber and an upper collet mechanism arranged to engage the drill string above the pressure chamber and a lower collet mechanism arranged to engage the drill string below the pressure chamber; and wherein said collet mechanisms are snubbers. 
 
     
     
       10. The drilling apparatus as claimed in  claim 1 , wherein the gripping mechanism comprises seals arranged to act on the drill string tool joint upset immediately adjacent to and above and below a blind ram or valve that segregates a pressure chamber into two parts; and wherein the pads and the seals are arranged to contact an upper upset and the apparatus comprises a lower gripping mechanism having grips and seals arranged to contact a lower drill string upset while leaving space for a blind ram or valve when a tool joint is connected. 
     
     
       11. The drilling apparatus as claimed in  claim 1 , wherein the collets and the pads are held in place by a keyway or ridge in the guide cylinders and are releasable by an additional rotation of the drive cylinder to facilitate inspection and replacement. 
     
     
       12. The drilling apparatus as claimed in  claim 1 , wherein the apparatus comprises a pressure chamber, an upper gripping mechanism arranged to engage a tubular or upset above the pressure chamber, and a lower gripping mechanism arranged to engage a tubular or upset below the pressure chamber; and
 wherein the apparatus further comprises a jack arranged to lift the upper gripping mechanism relative to the lower gripping mechanism to provide separation to inspect the gripping mechanisms; and 
 wherein the lower gripping mechanism comprises collets which are configured to support a tool joint box upset shoulder before collets of the upper mechanism are closed and lowered to interfere with a tool joint pin upset shoulder; and 
 wherein the collets provide a fail-safe support for the tool joint upset, such that the collets of the lower mechanism cannot retract until the drill string weight is taken off said collets and the collets of the upper mechanism cannot be retracted until the snubbing force is removed. 
 
     
     
       13. The drilling apparatus as claimed in  claim 1 , wherein the pad drive and the collet drive are related by differential gearing; and wherein the differential gearing comprises planet gears arranged such that movements of planet gears alters the rotary relationship between the drives. 
     
     
       14. A method of operation of a drilling apparatus on a rotary drilling rig with a top drive which enables circulation and rotation of a drill string to continue uninterrupted during the making of drill string connections,
 wherein the apparatus comprises a tool joint gripping mechanism arranged to rotate at the same speed as the drill string with an upset, and comprising: 
 gripping pads arranged to move radially relative to the drill string said gripping pads being wedge-shaped, with a tapered surface upon which a gripping force is exerted and a contact surface for contacting the drill string, 
 a pad drive to drive the pads radially relative to the drill string, 
 collets arranged to move radially with respect to the drill string, 
 a guide cylinder having ports for the pads and for the collets, and being adapted to rotate the pads and the collets and to restrain the pads and the collets to move radially, and 
 wherein the pad drive comprises a pad drive cylinder with internal wedge profiles which, on rotation relative to the pads when it rotates faster or slower than the guide cylinder, moves the pads radially to engage or disengage the drill string, wherein the method comprising steps of: 
 retarding or advancing the collets to move radially inwardly or outwardly, and 
 retarding or advancing the pad drive, causing the pads to move radially inwardly or outwardly. 
 
     
     
       15. The method as claimed in  claim 14 , wherein the apparatus is fixed to a rig floor and an extension sub in the drill string enables a bit to drill on during connections with a predetermined weight on the bit. 
     
     
       16. The method as claimed in  claim 14 , wherein a drill string pin upset is moved away from a drill string box upset by the depth of the pin plus a distance to allow a blind ram or a valve to close and to allow mud to flow into the drill string below and out of a tubular above. 
     
     
       17. The method as claimed in  claim 14 , wherein the apparatus is mounted on a hoist to allow vertical motion during connections and therefore enable continuous drilling. 
     
     
       18. The method as claimed in  claim 14 , wherein the apparatus comprises a pressure chamber and an upper gripping mechanism arranged to engage the drill string above a pressure chamber and a lower gripping mechanism arranged to engage the drill string below the pressure chamber.